Wood material panel pressing devices are used to compact fibrous press cakes or press them to produce wood material panels. In particular, the invention relates to continuously operating wood material panel pressing devices with which the fibrous press cake is continuously spread and pressed and/or compressed. This type of wood material panel pressing device is preferably operated at as high a speed as possible. However, high feed speeds, at which the fibrous press cake is moved through the wood material panel pressing device, lead to an increased likelihood of material defects. The fibrous press cake must therefore be compacted during pressing. However, this requires air being pressed out of the fibrous press cake. If this happens too quickly, the escaping air may tear fibers of the fibrous press cake, leading to crater-like ruptures. Such ruptures, which are also known as blow-outs, generally mean that the ruptured area of the wood material panel that has been produced cannot be used, thereby resulting in waste.
A further source of defects is a fluctuation of the fibrous press cake above a predetermined tolerance.
From DE 196 22 712 B4, DE 10 2007 019 390 A1 and DE 10 2005 049 880 A1 it is known to allow thin metal wires to slide over the fibrous press cake, said wires establishing electrical contact with a press plate of the one pressing device when the thickness of the fibrous press cake exceeds a predetermined maximum thickness. The disadvantage of this system is that it only allows for a binary monitoring, namely whether the maximum thickness has been exceeded. A further disadvantage is that ruptures, as described above, are only detected if they occur immediately beneath a wire.
WO 2009/071738 A1 describes a press system for gluing wooden rods together to produce edge-glued panels. To ensure a uniform adhesion, a thermographic image is captured by a thermal camera after gluing. If the temperature of the finished edge-glued panel deviates considerably, even just locally as the case may be, from a predetermined temperature, the heat output of the press system is corrected. To achieve an especially precise measurement result, the temperature of the arranged wooden rods can also be measured prior to gluing by means of a thermal camera. This renders it possible to determine where the local heat output of the press system is too low. This type of press system is unsuitable for the pressing of fibrous press cakes to produce wood material panels, as a fibrous press cake requires a high surface pressure and cannot withstand lateral pressure. Furthermore, only the (local) heat output can be controlled or regulated with such a system; it is thus unsuitable for preventing blow-outs.